Multi-stage Dockerfile for compilation and runtime

[EliRibble]

I'm interested in building Cloudreve myself and running it. There's already a Dockerfile in the project which is used to take the already compiled build output and structure it for deployment. With a few changes this could be a multi-stage dockerfile which works both for building and for deployment, without bloating the resulting image.

[HFO4]

I actually prefere goreleaser to pre-build all binaries and build multi-arch images. We need to ship those binaries+images in each release, so it's faster to reuse fresh binaries for docker images.